Research Focus: Cognitive Impairment in Schizophrenia
The hidden symptoms of schizophrenia
Cognitive deficits are the less dramatic and less known, but equally disabling symptoms that accompany psychosis for many people living with schizophrenia. Most people with schizophrenia experience problems with basic cognition—the mental functions that help us perform even simple tasks of everyday life. These symptoms can make it hard to live independently, have a job or go to school, or socialize with others.
For most, the auditory hallucinations or delusions of psychosis can be treated with varying degrees of success and side effects, using medications. But there is virtually no treatment available to address the cognitive impairments of schizophrenia. (The exception may be the drug clozapine, which some researchers are convinced can improve cognition, even if it is only relatively small boost.) And unlike psychosis, cognitive impairment does not come and go, or get better over time, but seems to remain pretty constant. (Cognitive impairment can also be a symptom in bipolar disorder and major depressive disorder, to a somewhat lesser degree, and is equally difficult to treat.)
The cognitive impairments of schizophrenia most commonly include:
- Trouble focusing or paying attention
- Difficulty processing information quickly
- Problems with “working memory” (the ability to store and use information in the short term)
Working memory seems to be the most common and the strongest problem for people living with schizophrenia, and this is a crucial brain function for everyday life. We use working memory throughout the day, anytime we need to hold a thought or new piece of information in our brains for a short period of time. You can think of it as the brain’s notepad—pieces of paper that are quickly recycled unless the information is important enough to be transferred and stored elsewhere.
If you go into another room only to forget what you were there for, your working memory has failed you. We are even using working memory in a casual conversation, when we have a thought we want to express, but wait for someone else to finish talking before we speak up. Indeed, as you read this article, you need working memory to tie sentences together and generate meaning.
It’s not really surprising, then, that problems with cognition often affect the life of a person living with schizophrenia more than the degree of psychosis he or she experiences. In fact, overall, the degree of cognitive impairment is a stronger predictor of difficulties working or living independently than psychosis or even negative symptoms (which are also difficult to treat, and contribute to difficulty in daily life). Finding effective treatments for cognitive impairments in schizophrenia has thus been a high priority in the research community.
Treatments on the horizon?
Currently, there is evidence that some forms of psychotherapy, specifically “cognitive rehabilitation” therapies, might be effective for cognitive deficits of schizophrenia. But there are many forms of cognitive rehabilitation, and we still don’t know which are most effective (and for which people). The kind of research needed to figure that out is very difficult, as there are so many variables that need to be accounted for, including what is considered “effective.” Sometimes, people who have had cognitive rehabilitation have shown improvement in cognitive tests without having much improvement in “functional outcome”—that is, benefits in their daily lives. A recent paper that surveyed different studies of cognitive remediation therapies found that functional outcomes were better when “individuals are given opportunities to practice the cognitive skills in real-world settings.” A good overview of cognitive rehabilitation therapies (written for providers) also emphasizes the importance of combining cognitive treatments with broader functional treatment.
A study in Denmark, called FOCUS, is examining whether cognitive remediation provided early can help people at “ultra high risk” for schizophrenia—that is, people who are showing early signs of (but not full-blown) psychosis and cognitive deficits.
In addition, there are some medications that have potential for treating cognitive symptoms of schizophrenia. Memantine, a drug used to treat Alzheimer’s, has been used “off-label” to treat people with schizophrenia, with some clinicians reporting success. In large controlled trials, however, memantine has yet to show success in schizophrenia, but research is still going on. It may be that some people would benefit more than others, and we would need a way to identify those people. Another drug, encenicline, has shown promise in clinical trials in improving cognitive functions for people with schizophrenia, and is being studied further for both schizophrenia and Alzheimer’s.
In the meantime, researchers are still trying to understand better the brain mechanisms underlying the cognitive difficulties that prevent better recovery for so many people with schizophrenia.
Three recent studies, for example, looked at a certain type of neuron in the frontal cortex of the brain—the parvalbumin or PV neuron—which has already been thought to play a big role in cognitive deficits when it is not functioning correctly. These studies all demonstrated different ways in which PV neurons might be involved in cognitive impairment. If that sounds like we still have a lot to learn about why and how the brain produces the cognitive impairments of schizophrenia, you’re right—we do.
In the short term, we can hope to find treatments that seem to help even though we don’t know why—after all, that is the case for many of the treatments we use for many disorders and diseases, including the mental illnesses.